Micro mirror and method for fabricating the same

ABSTRACT

A micro mirror structure having an increased driving angle while being driven in high speed. The micro mirror includes a rotatable mirror section that reflects light, a pair of spring sections for supporting the mirror section and serving as a rotational axis for the mirror section when the mirror section is rotationally driven, an oval adjoining section for connecting the mirror section and the pair of spring sections, and a driving section including mobile combs arranged on the adjoining section. A fixed comb is provided above and/or below the mobile combs to correspond to the mobile combs to generate electrostatic force. According to the present invention, by existence of the oval adjoining section, moment can be increased without largely increasing rotational inertia moment. Therefore, a high-speed optical scanner with an increased driving angle can be provided, which is required for a high-resolution laser TV.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Application No.2003-86624, filed Dec. 2, 2003 in the Korean Intellectual PropertyOffice, the disclosure of which is incorporated herein in its entiretyby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Apparatuses and methods consistent with the present invention relate toa micro mirror, and in particular, to a micro mirror capable of beingused as an optical scanner for scanning laser beams in a display devicesuch as a laser TV, and a method for fabricating the same.

2. Description of the Related Art

As the age of multimedia has arrived, the demand for large displays hasincreased and various types of large-display devices are beingsuccessively introduced. A laser TV is proposed as a display device forthe next generation that can implement high-resolution at a low priceand provide a large size.

Such a laser TV includes an optical scanner that scans laser beamsprojected from a laser diode module in horizontal and verticaldirections according to RGB image signals. The optical scanner includesa micro mirror fabricated on the basis of Micro-Electro MechanicalSystem (MEMS).

FIGS. 1A and 1B schematically illustrate different types of micromirrors publicly known in the prior art, and FIG. 2 is a drawing fordescribing the operations of these micro mirrors.

As can be seen from the drawings, a micro mirror comprises a rotatablemirror section 1, a pair of spring sections 2 and 2′ connected to themirror section 1 to support the mirror section 1 and to serve as arotation axis when the mirror section 1 rotates, a mobile comb 3, and afixed comb 4.

The mobile comb 3 and the fixed comb 4 have a plurality of comb-fingers3 a, 3 b, . . . ; 4 a, 4 b, . . . , respectively. The mobile comb 3 maybe installed either on the mirror section 1 as shown in FIG. 1A or onthe spring sections 2 and 2′ as shown in FIG. 1B. The fixed comb 4 maybe installed above or below the mobile comb 3, as shown in FIG. 2,wherein they are arranged in such a manner that the comb-fingers 3 a, 3b, . . . of the mobile comb 3 and the comb-fingers 4 a, 4 b, . . . ofthe fixed comb 4 clasp each other.

Therefore, if plus (+) voltage is applied to one side comb-fingers 4 aamong the comb-fingers 4 a, 4 b of the fixed comb 4 corresponding to thecomb-fingers 3 a, 3 b of the mobile comb 3 electrified to minus (−),electrostatic force is generated between the comb-fingers 3 a and 4 a,and accordingly, the mirror section 1 is rotationally driven about thespring sections 2 and 2′, as indicated by dotted lines in FIG. 2.Whereas, if plus (+) voltage is applied to the other side comb-fingers 4b, the mirror section 1 is rotationally driven in the reverse direction.Due to this rotational driving of the mirror section 1, incident lightis scanned to a scanning surface while being continuously and uniformlyreflected to a predetermined angle range.

The driving velocity of the micro mirror is related to resolution of adisplay device, and the driving angle is related to a picture screensize of such a display device. That is, as the driving velocity of themicro mirror is increased, the resolution is also increased, and as thedriving angle is increased, the picture screen is also increased.Therefore, in order to implement a large high-resolution laser TV, anoptical scanner such as a micro mirror is required which has anincreased driving angle while being driven at high velocity.

However, since driving velocity and driving angle of a micro mirrorconflict with each other, there is difficulty in increasing drivingangle of a micro mirror and the driving velocity thereof at the sametime. Resonance driving may be used in order to increase a driving angleof a micro mirror. However, this has a problem in that the yield ofproduction is very low since it is very difficult to match the naturalfrequency of a micro mirror with a driving frequency due to errors infabrication, and thus a tuning structure is required for tuning thedriving frequency.

In a conventional micro mirror as shown in FIG. 1A, the mobile comb 3 isarranged on the opposite sides of a mirror section 1, in which casesince a distance D₁ from the rotational center of the mirror section 1is long, a moment is increased as compared to the case in which the combfingers of the mobile combs 3 are arranged on the spring sections 2 and2′ as shown in FIG. 1B, if the same number of comb-fingers are employed.However, in this case, the number of mobile combs 3 is limited, and inaddition, the size of mirror section 1 is increased in order to providean increased number of comb-fingers of a mobile comb 3, and thus theinertia moment will be increased, and the natural frequency of themirror will be lowered. Accordingly, driving velocity can not beincreased.

Meanwhile, in a micro mirror as shown in FIG. 1B, the mobile combs 3 arearranged on spring sections 2 and 2′, in which case it is possible toreduce the magnitude of rotational inertia moment while increasing thenumber of mobile combs 3, as compared to the mirror having the structureshown in FIG. 1A. However, it is impossible to obtain a sufficientdriving angle since the distance D₂ from the central axis of the mirrorsection is short, thereby generating low moment. In addition, this casehas a problem in that the rigidity of the spring sections 2 and 2′ isnot uniform due to a process error or the like.

Thus, in the conventional micro mirrors as described above it is hard toprovide a high driving velocity and an increased driving angle due totheir constructions. Therefore, the conventional micro mirrors are notsuitable for an optical scanner for a large high-resolution laser TV.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been conceived to solve theabove-mentioned problems occurring in the prior art, and an aspect ofthe present invention is to provide an improved micro mirror to increasemoment while reducing rotational inertia moment so that the micro mirrorcan be used as a high-speed optical scanner having an increased drivingangle, and a method for fabricating the same.

According to a non-limiting, illustrative embodiment of the presentinvention, there is provided a micro mirror comprising a rotatablemirror section that reflects light, a pair of spring sections forsupporting the mirror section and serving as a rotational axis for themirror section when the mirror section is rotated, an adjoining sectionfor connecting the mirror section and the pair of spring sections. Adriving section is provided comprising a mobile comb mounted in theadjoining section and a fixed comb disposed corresponding to the mobilecomb to generate electrostatic force.

The mirror section may be formed in a circular shape for reflectinglight with a minimum area, however, the shape is not limited so.

The adjoining section may be formed in an oval shape because more mobilecombs can be provided thereon and the oval shape is advantageous in viewof rotational inertia moment. However, the shape is not limited so.

According to an embodiment of the present invention, the micro mirror ispositioned in such a manner that its minor axis portion is circumscribedto the circumference of the circular mirror section.

The pair of spring sections perform torsional motion when the mirrorsection is rotated. The mobile comb and the fixed comb of the drivingsection are provided with a plurality of comb-fingers, respectively, andthese fingers are correspondingly arranged to clasp one another. It isalso contemplated that the fingers of the mobile comb may be arranged onthe outer periphery of the adjoining section, or on both of the innerand outer peripheries of the adjoining section. Further, the fingers ofthe mobile comb may be arranged on the inner and/or outer periphery andon both sides of the pair of spring sections.

In addition, the fixed comb may be arranged both above and below themobile comb. If the fixed comb is arranged both above and below themobile comb, the driving angle of the mirror section can be furtherincreased because more increased electrostatic force can be appliedbetween the one mobile comb and fixed comb.

According to another aspect of the present invention, there is provideda micro mirror comprising a rotatable mirror section that reflectslight; a pair of spring sections for supporting the mirror section andserving as a rotational axis for the mirror section when the mirrorsection is rotationally driven; a first adjoining section for connectingthe mirror section and the pair of spring sections. It is contemplatedthat the first adjoining section is arranged to be circumscribed to thecircumference of the mirror section in one diametrical direction andconnected to the pair of spring sections in another diametricaldirection. A second adjoining section is connected to a connectionportion between the pair of spring sections of the first adjoiningsection with one end, and connected to the mirror section at the portionopposed to the connection portion with the other end. A driving sectionis provided that comprises a mobile comb arranged on the first adjoiningsection, and a fixed comb provided above or below the mobile combs tocorrespond to the mobile combs to generate electrostatic force.

It is preferable but not limited to or necessary to form the mirrorsection in a circular shape, the first adjoining section in an ovalshape, and each second adjoining section in a straight-line shape.

The fingers of the mobile comb may be arranged on the periphery of thefirst adjoining section, on both of the inner and outer peripheries ofthe first adjoining section, or on the opposite sides of the pair of thesecond adjoining sections. In addition, fingers of the fixed comb may beadditionally arranged on the opposite sides of the pair of the springsections. Further, the fixed comb may be arranged both above and belowthe mobile comb.

In order to achieve the afore-mentioned aspect of the present invention,there is also provided a method for fabricating a micro mirrorcomprising steps of forming a first metal electrode on a first glass, b)forming a first fixed comb on a first wafer through a predeterminedprocess, c) bonding the first glass and the first wafer, and polishingthe first wafer to a mirror thickness, d) forming a mirror section, aspring section, an adjoining section and a mobile comb in the firstwafer polished to the mirror thickness, through a predetermined process,e) bonding a second glass patterned to form a second metal electrode anda second wafer patterned to form a second fixed comb, and polishing thesecond wafer to a comb thickness after bonding the second glass and thesecond wafer, f) forming the second metal electrode on the second glassthrough the patterning of the second glass, g) forming the second fixedcomb on the second wafer polished to a comb thickness through apredetermined process, and h) assembling a subassembly of step d) and asubassembly of step g) by bonding, and then bonding first and secondwires for applying driving voltage to the first and second metalelectrodes.

Step a) comprises steps of providing a Pyrex glass having apredetermined thickness, forming a line hole for the first metalelectrode on the glass by etching, coating a metal layer to apredetermined thickness on the surface of the glass having the linehole, and removing the metal layer by etching except the metal layerabove the line hole.

Step b) comprises steps of providing a highly doped SOI wafer having asilicone layer of a predetermined thickness, a single crystal siliconlayer and a SiO₂ layer interposed between the silicon layers, andforming a plurality of comb-fingers of the first fixed comb in thesingle crystal silicon layer through a photolithography process.

In addition, step d) comprises step of forming an Au reflection part forreflecting light on the surface of the mirror section, wherein themirror section, spring sections, adjoining section, and mobile sectionsare formed by a photolithography process.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the presentinvention will be more apparent from the following detailed descriptiontaken with reference to the accompanying drawings, in which:

FIGS. 1A and 1B are top plan views schematically showing the structureof a conventional micro mirror;

FIG. 2 is a view for illustrating the operation of the micro mirrorsshown in FIG. 1;

FIG. 3 is a perspective view schematically showing the structure of amicro mirror according to a first non-limiting, illustrative embodimentof the present invention;

FIGS. 4A and 4B are schematic views for illustrating the operation ofthe micro mirror according to the first embodiment as shown in FIG. 3,in which FIG. 4A shows an application of a fixed comb provided below amobile comb, and FIG. 4B shows an application of two fixed combsprovided above and below a mobile comb;

FIG. 5 is a perspective view schematically showing a construction of amicro mirror according to a second exemplary embodiment of the presentinvention;

FIG. 6 is a perspective view schematically showing a construction of amicro mirror according to a third exemplary embodiment of the presentinvention;

FIG. 7 is a perspective view schematically showing a construction of amicro mirror according to a fourth exemplary embodiment of the presentinvention;

FIG. 8 is a perspective view schematically showing a construction of amicro mirror according to a fifth exemplary embodiment of the presentinvention;

FIG. 9 is a perspective view schematically showing a construction of amicro mirror according to a sixth exemplary embodiment of the presentinvention;

FIG. 10 is a perspective view schematically showing a construction of amicro mirror according to a seventh exemplary embodiment of the presentinvention;

FIG. 11 is a perspective view schematically showing a construction of amicro mirror according to an eighth exemplary embodiment of the presentinvention;

FIGS. 12A to 12F illustrate a process of fabricating a lower structureof a micro mirror according to the present invention;

FIGS. 13A to 13F illustrate a process of fabricating an upper structureof a micro mirror according to the present invention; and

FIG. 14 shows the lower structure and the upper structure fabricatedaccording to the processes as shown in FIGS. 12A–F and 13A–F,respectively, in an assembled state.

DETAILED DESCRIPTION OF EXEMPLARY, NON-LIMITING Embodiments

As shown in FIGS. 3, 4A and 4B, a mirror section 10 for reflecting lightin a micro mirror according to a first embodiment of the presentinvention is formed in a circular shape having a minimum area forreflecting light. Although the mirror section 10 is not limited to acircular shape, the circular shape does not increase rotational inertiamoment so largely. The radius of the mirror section 10 can be properlyadjusted depending on a radius of light to be used.

Such a mirror is rotationally driven within a predetermined angularrange about a pair of spring sections 20 and 20′. The pair of springs 20and 20′ support the mirror section and perform torsion motion when themirror section 10 is rotationally driven.

An adjoining section 30 connects the mirror section 10 and the pair ofspring sections 20 and 20′. The adjoining section 30 is formed in anoval shape, and the mirror section 10 is positioned within the adjoiningsection 30. The minor axis portions on the inner periphery of the ovaladjoining section 30 and the corresponding parts on the outer peripheryof the mirror section 10 are connected with each other. The major axisportions of the adjoining section 30 are connected to the pair of springsections 20 and 20′, respectively. With this arrangement of the mirrorsection 10 and the adjoining section 30, predetermined spaces areprovided within the oval adjoining section 30, that is, between theinner periphery portion of the adjoining section 30 extended from theminor axis to the major axis thereof and the non-circumscribed outerperiphery portion of the mirror section 10.

The shape of the adjoining section 30 is not limited to an oval shape.However, the oval shape allows more comb-fingers to be installed on theadjoining section 30 and does not increase rotational inertia moment solargely so that the driving angle of the micro mirror can be maximized.

A mobile comb 40 comprises a plurality of comb-fingers 40 a, 40 b, andthe comb-fingers 40 a, 40 b are equi-spaced around the circumstance ofthe oval adjoining section 30. Compared to a conventional structure, inthe present embodiment, the area of the mirror section or the likeaffecting rotational inertia moment is rather reduced while allowingmore comb-fingers to be arranged on the mobile comb 40 as compared to aconventional one.

A fixed comb 50 is also provided that has a plurality of comb-fingers 50a, 50 b, respectively, in which the comb-fingers 50 a, 50 b are arrangedbelow the mobile comb 40 as can be seen from FIG. 4A. At this time, thecomb fingers 40 a, 40 b of the mobile comb 40 and the comb fingers 50 a,50 b of the fixed comb 50 are arranged to clasp one another.Alternatively, the fixed comb 50 may be disposed above the mobile comb40.

As shown in FIG. 4B, it is possible to provide an embodiment in which afirst fixed comb 50 is arranged below the mobile comb 40, and a secondfixed comb 50′ is arranged above the mobile comb 40.

In the mirrors as described above, electrostatic force is applied to themobile comb 40 arranged on the adjoining section by the fixed comb 50installed to be engaged with the mobile comb 40, as shown in FIG. 4A.The electrostatic force induces rotational force, in which the springsections 20 and 20′ of the mirror section 10 serve as a center axis forthe rotational force. Accordingly, the mirror section 10 rotates aboutthe spring sections 20 and 20′, and if the voltage of the fixed comb 50is applied in a constant driving frequency, the mirror section 10 willbe repeatedly rotated with the driving frequency.

The micro mirror as shown in FIG. 4B has first and second fixed combs50, 50′ arranged above and below the mobile comb 40, respectively. Inthis case, since the electrostatic force between the mobile comb 40 andthe fixed combs 50, 50′ is doubled as compared to the case shown in FIG.4A, a more increased driving angle of the mirror can be obtained. Inaddition, since the electrostatic force is equally applied to the mirrorsection 10 in up and down directions, the mirror section can be smoothlydriven without being vibrated up and down.

As described above, a micro mirror construction proposed by the presentinvention has an increased driving angle and high natural frequency ascompared to the conventional micro mirror. Therefore, the inventivemicro mirror can accomplish an increased driving angle while beingdriven in high velocity, the principle of which will be described usinga following equation.

If any attenuation component is disregarded, motion of a rotating bodymay be expressed by the following equation:J{umlaut over (θ)}+kθ=M

-   wherein J is a rotational inertia moment, k is a torsional spring    constant, and M is an applied torque.

The natural frequency for the rotational motion of this system isexpressed as follows:

$f = {\frac{1}{2\pi}\sqrt{\frac{k}{J}}}$

According to the above equations, with micro mirrors designed to havethe same natural frequency, if the rotational inertia moment J isreduced, the torsional spring constant k can be reduced, and therefore,the driving angle can be increased even with small force.

As a result of analyzing a conventional construction and an inventiveconstruction using an ANSYS program for computer simulation, when thetwo constructions are driven with the same driving frequency (33.75 KHz)after designing the constructions each to have a natural frequency of 40KHz, the driving angle of the conventional one is 2.3 degrees while thatof the inventive one is 4.0 degrees.

FIG. 5 shows a micro mirror according to a second embodiment of thepresent invention.

As shown in the drawing, the basic construction and operation of themicro mirror according to the second embodiment is the same as that ofthe first embodiment described above. Therefore, the similar parts areindicated by similar reference numerals. However, detailed descriptionthereof is omitted, and only the characteristic construction of thisembodiment is described. Other various embodiments will be shown anddescribed later in this manner.

As shown in FIG. 5, in the present embodiment, the mobile combs 140 arearranged on the inner periphery as well as on the outer periphery of theoval adjoining section 130. The adjoining section 130 connects themirror section 110 and the pair of spring sections 120 and 120′.Although not specifically shown, the fixed combs are provided aboveand/or below the mobile combs 140 to correspond to the mobile combs 140.In addition, the fixed combs may be arranged above and/or below themobile combs 140.

In a micro mirror according to a third embodiment of the presentinvention as shown in FIG. 6, mobile combs 240 are provided on the outerperiphery of an oval adjoining section 230 and on opposite sides ofspring sections 220 and 220′. The adjoining section 230 connects themirror section 210 and the pair of spring sections 220 and 220′. Inaddition, although not shown in the drawing, mobile combs may beadditionally provided on the inner periphery of the adjoining section230. As would be appreciated by one skilled in the art, fixed combs maybe installed above and/or below the respective mobile combs in this andlater embodiments, in a manner similar to that described in regard toFIGS. 4A and 4B.

FIG. 7 shows a micro mirror according to a fourth embodiment of thepresent invention. As shown in FIG. 7, the fourth embodiment of thepresent invention comprises a circular mirror section 310, a pair ofspring sections 320 and 320′, a first adjoining section 330 of an ovalshape, a pair of second adjoining sections 330 a and 330 b having astraight line shape extended from the portions where the spring sections320 and 320′ are adjoined to the first adjoining section 330, to themirror section 310. The mobile combs 340 and fixed combs construct adriving section. The mobile combs 340 are arranged on the outerperiphery of the first adjoining section 330 and on the opposite sidesof each second adjoining section 330 a and 330 b.

In addition, a micro mirror according to a fifth embodiment of thepresent invention, as shown in FIG. 8, has a mirror section 410, a pairof spring sections 420 and 420′, and a pair of second adjoining sections430 a and 430 b. Mobile combs 440 are arranged on the inner and outerperipheries of the first adjoining section 430 unlike the fourthembodiment.

FIGS. 9 to 11 respectively show sixth to eighth embodiments. The sixthembodiment of FIG. 9 is a micro mirror provided with mobile combs 540 onthe periphery of a first adjoining section 530 and on the opposite sidesof a pair of spring sections 520 and 520′ thereof, respectively. Amirror section 510 is provided along with a pair of second adjoiningsections 530 a and 530 b. The seventh embodiment of FIG. 10 is a micromirror provided with a mirror section 610. Mobile combs 640 are disposedon the outer periphery of a first adjoining section 630, on the oppositesides of a pair of spring sections 620 and 620′ and on the oppositesides of each second adjoining section 630 a and 630 b, respectively.Additionally, the eighth embodiment of FIG. 11 is a micro mirrorprovided with mobile combs 740 on the inner and outer peripheries of afirst adjoining section 730 and on the opposite sides of a pair ofsprings 720 and 720′, respectively. A mirror section 710 is alsoprovided along with a pair of second adjoining sections 730 a and 730 b.

As can be seen from the constructions of the various embodiments above,the inventive mirrors commonly have an oval adjoining section which doesnot increase rotational inertia moment so largely while the area of acircular mirror section can be minimized and more mobile combs can beprovided on the adjoining section. Accordingly, it is possible toimplement an increased driving angle while increasing driving velocityof a micro mirror.

Hereinbelow, a method of fabricating the inventive micro mirror will bedescribed with reference to FIGS. 12 to 14. In this embodiment, a methodof fabricating a micro mirror in which first and second fixed combs arearranged above and below a mobile comb is described.

FIGS. 12A to 12F show steps of fabricating a lower structure of a micromirror.

First, first metal electrodes 811 and 812 are formed on a first glass810 having a predetermined thickness, as shown in FIG. 12A. A Pyrexglass may be used for the glass 810. The metal electrodes 811 and 812may be formed through steps of etching electrode-forming areas on thefirst glass 810 to form line holes for the metal electrodes 811 and 812,coating an electrode metal layer on the entire surface of the glass 810to a predetermined thickness, and wet-etching the electrode metal layerto leave the metal layer only on the line holes.

After preparing the first glass 810 having metal electrodes 811 and 812as described above, a first wafer 820 is provided as shown in FIG. 12B.The first wafer 820 is a highly doped SOI wafer having a silicon layer821 of a predetermined thickness, a single crystal silicon layer 822 anda SiO₂ layer 823 interposed between the silicon layer 821 and the SiO2layer 823.

The single crystal silicon layer 822 of the first wafer 820 is formedwith a plurality of comb-fingers 824 which form a first fixed comb. Theplurality of comb-fingers 824 may be formed by a photolithographyprocess, for example.

FIG. 12D shows a state in which the silicon layer 821 of the first wafer820 is polished to a certain thickness for forming a mirror after thefirst glass 810 and the first wafer 820 are bonded to each other. Thecertain thickness may be set within a range approximately of 50 μm˜200μm.

On the surface of the polished silicon layer 821 of the first wafer 820,bonding areas 825 and 825′, and a reflection area 826 are formed atproper positions. Both of the bonding areas 825 and 825′ and thereflection area 826 are formed from Au, by depositing Au on the siliconlayer 821 to a predetermined thickness and then etching the Au layer toremove a useless area.

As can be seen from FIG. 12F, a mirror section 827, spring sections 828,mobile comb 829, and an adjoining section (not shown) are formed in thesilicon layer 821 through a photolithography process, for example.

FIGS. 13A to 13F illustrate steps of fabricating an upper structure of amicro mirror.

FIG. 13A and FIG. 13B show a second wafer 830 and a second glass 840,respectively. The second wafer 830 is a highly doped silicon wafer, andthe second glass 840 has a DFR film 841. The second wafer 830 has apattern section 831 for forming a second fixed comb, and the secondglass 840 also has a pattern section 842 patterned to form second metalelectrodes 843 and 844.

The second wafer 830 and the second glass 840 are bonded to each otheras shown in FIG. 13C, and then predetermined second electrodes 843 and844 are formed through the pattern section 842 of the second glass 840,as shown in FIG. 13D. The second metal electrodes 843 and 844 are formedby patterning the electrodes using a mask after coating a metal layer.

FIG. 13E shows bonding parts 832 and 832′ formed on predeterminedpositions on the second wafer 830. The bonding parts 832 and 832′ areformed by depositing Au on the surface of the second wafer, plating AuSnand then removing useless deposited layer and plated layer. Then, aplurality of comb-fingers 833 forming a second fixed comb are formed onthe second wafer 830 as shown in FIG. 13F through a photolithographyprocess, for example.

The lower structure and the upper structure each fabricated through theprocesses as described above are assembled by using bonding parts 825,825′, 832 and 832′ formed on the respective structures, as shown in FIG.14.

Finally, first and second wires (not shown) are bonded to apply drivingvoltage to the first and second metal electrodes 811 and 812, 843, 844of the first and second glasses 810 and 840 in the structure assembledas described above.

As described above, according to the present invention, a micro mirroris implemented, which is capable of increasing moment without increasingrotational inertia moment so largely. Accordingly, a high-speed opticalscanner with an increased driving angle can be provided such that itwill be possible to accelerate development of next generation displaydevices such as a laser TV and marketing of products thereof.

While the embodiments of the present invention have been shown anddescribed with reference to the embodiments thereof in order toexemplify the principle of the present invention, the present inventionis not limited to the embodiments. It will be understood that variousmodifications and changes can be made by those skilled in the artwithout departing from the spirit and scope of the invention as definedby the appended claims. Therefore, it shall be considered that suchmodifications, changes and equivalents thereof are all included withinthe scope of the present invention.

1. A micro mirror comprising: a rotatable mirror section that reflectslight; a pair of spring sections which support the mirror section andserve as a rotational axis for the mirror section when the mirrorsection is rotationally driven; an adjoining section which connects themirror section and the pair of spring sections the adjoining sectionhaving a curved periphery; and a driving section comprising a mobilecomb, and a fixed comb which generates electrostatic force, wherein thefixed comb is positioned above or below the mobile comb to correspond tothe mobile comb, wherein the mobile comb comprises fingers extended fromthe curved periphery of the adjoining section.
 2. The micro mirroraccording to claim 1, wherein the mirror section has a circular shape.3. The micro mirror according to claim 1, wherein the adjoining sectionhas an oval shape.
 4. The micro mirror according to claim 1, wherein themirror section has a circular shape and the adjoining section has anoval shape, and wherein the adjoining section is positioned in such amanner that its minor axis portions are circumscribed to thecircumference of the mirror section.
 5. The micro mirror according toclaim 1, wherein the pair of spring sections perform torsional motionwhen the mirror section is rotationally driven.
 6. The micro mirroraccording to claim 1, wherein the fingers of the mobile comb arearranged on the outer periphery of the adjoining section.
 7. The micromirror according to claim 1, wherein the fingers of the mobile comb arearranged on both of inner and outer peripheries of the adjoiningsection.
 8. The micro mirror according to claim 1, wherein the fixedcomb is arranged above the mobile comb and another fixed comb isarranged below the mobile comb.
 9. The micro mirror according to claim1, wherein at least a portion of the curved periphery of the adjoiningsection is spaced apart from the mirror by an open space.
 10. The micromirror according to claim 1, wherein the mirror merges with theadjoining section at a first location, and the fingers of the mobilecomb are shorter at the first location than other locations at ends ofthe adjoining section.
 11. The micro mirror according to claim 1,wherein the adjoining section forms a path which is tangential to themirror.
 12. A micro mirror comprising: a rotatable mirror section thatreflects light; a pair of spring sections which support the mirrorsection and serve as a rotational axis for the mirror section when themirror section is rotationally driven; an adjoining section whichconnects the mirror section and the pair of spring sections, theadjoining section having a curved periphery; and a driving sectioncomprising mobile combs with fingers arranged on the curved periphery ofthe adjoining section and on the pair of spring sections, respectively,and fixed combs provided at least one of above and below the mobilecombs to correspond to the mobile combs to generate electrostatic force.13. The micro mirror according to claim 12, wherein at least a portionof the curved periphery of the adjoining section is spaced apart fromthe mirror by an open space.
 14. The micro mirror according to claim 12,wherein the mirror merges with the adjoining section at a firstlocation, and the fingers of the mobile comb are shorter at the firstlocation than other locations at ends of the adjoining section.
 15. Themicro mirror according to claim 12, wherein the adjoining section formsa path which is tangential to the mirror.